The invention relates to a seat belt retractor.
In a conventional seat belt retractor a belt reel is rotatably mounted on a frame for coiling and uncoiling the seat belt, a motive spring is able to act on the belt reel in the coiling direction. A blocking device is provided for blocking rotation of the belt reel, in particular in the case of excessive acceleration or deceleration of the vehicle, for example in the case of an accident. This can be achieved in that a blocking pawl, supported on the frame and having corresponding teeth, is brought into engagement with the belt reel, or blocking teeth provided on the belt reel are brought into blocking engagement with corresponding teeth on the frame. The movement between the pawl and the belt reel or between the belt reel and the frame required for this purpose is brought about by a control member which can be activated in response to the belt webbing and/or in response to the vehicle (i.e. in a belt webbing-sensitive and/or a vehicle-sensitive manner). A belt sensor mass which is movably mounted on a carrier member rotating with the belt reel is provided for activation of the control member in response to the speed at which the belt webbing is protracted from the retractor. A vehicle sensor mass is provided for activation of the control member in response to the vehicle deceleration. Both the belt sensor mass and the vehicle sensor mass actuate a coupling device, for example in the form of movable coupling elements on the carrier member and control member, by means of which a moving connection between carrier member and control member is produced in order to transmit a rotation of the belt reel in the uncoiling direction for actuating the blocking device.
In order to transmit the movement of rotation of the belt reel in the uncoiling direction to actuate the blocking device for controlled blocking engagement of the belt reel on the frame or of a blocking element, in particular blocking pawl, supported on the frame into the belt reel, it is necessary with known seat belt retractors to maintain exact tolerances of a movement-transmitting means and the blocking engagement elements with respect to the belt reel. This necessitates high production costs, in particular during assembly of the components provided on the mechanical side of the belt retractor.
It is accordingly an object of the invention to create a seat belt retractor of the type mentioned at the outset in which the fitting, in particular of the components provided on the mechanical side, is simplified.
With the invention, a preassembled unit consisting of the carrier member and the belt sensor mass mounted thereon and the control member is provided. These components can be preassembled in an exact orientation relative to one another, in particular with respect to a common axis which coincides with the reel axis after assembly. Both the belt sensor mass and the carrier member and the control member are mounted on one another rotatably about this common axis in the unit. The carrier member and the control member are preferably connected rotatably relative to one another to the unit by a plug-in connection forming a pivot bearing.
The control member preferably possesses a rim which surrounds the unit and on which clip elements are arranged. These clip elements can be clipped into correspondingly designed clip elements of a holder about the common axis rotatably in the holder. The holder with the unit mounted rotatably therein surrounds the entire mechanical side of the belt retractor. This consists of the components which respond to the vehicle and to the belt webbing, of the carrier for the belt webbing sensor which is connected non-rotatably to the belt reel when the holder is plugged onto the frame with the belt reel, and the control member which is mounted rotatably in the holder and can be coupled to the carrier member designed, in particular, as a ratchet wheel so as to respond to the belt webbing and/or vehicle by means of corresponding coupling elements.
To produce the rotational connection between the carrier member and the belt reel, projections and associated recesses can be provided on the carrier member and the belt reel which are plugged into one another.
The invention also provides a seat belt of the type mentioned at the outset with which forces acting, in particular, during tensioning of the belt webbing due to accelerated rotation of the belt reel on the coupling element mounted on the carrier member and actuated by the belt sensor mass do not affect the coupling function.
In this embodiment, a coupling element actuated by the belt sensor mass, in particular in the form of a two-sided lever of the type known from DE 195 01 679 A1, incorporated herein by reference, is movably mounted on the carrier member by means of an impact energy-absorbing bearing. Owing to the impact absorbing-properties of the bearing for the coupling element, the forces acting on the coupling element during tensioning of the belt webbing due to an accelerated rotational drive of the belt reel, do not adversely affect the coupling function. Varying loads occurring during tensioning, in particular at the beginning of tensioning or during a changeover between the individual driving stages in the case of multi-stage tensioner drive and at the end of the tensioning process are cushioned by the energy-absorbing bearing of the coupling element so that the coupling element and the coupling parts, in particular the teeth of the control member in which the coupling element engages, with its engagement part designed, in particular, as a pawl, are not damaged.
For forming the impact energy-absorbing bearing, one or more shock-absorbing bearing faces can be provided on the coupling element, in particular as a function of the main loading direction. If loads occur in several directions or within a greater angular range, several shock-absorbing bearing faces are provided. In a preferred embodiment, three or more flexible rectilinear bearing faces which are arranged in an equilateral polygon, in particular a triangle, will be disposed round a central point. In the disengaged coupling position of the coupling element, the flexible bearing faces lie on rounded bearing positions of a bearing pin fastened on the carrier member in the centre of the triangle. In the engaged position of the coupling element, i.e. when the coupling element engages in the associated coupling element on the control member, for example in the form of teeth, the flexible rectilinear bearing faces of the coupling element lie flat on support faces of the bearing pin which then extend approximately in parallel. These support faces are formed, for example, by projections on the bearing pin which are arranged at equal angular pitch round the pivot axis of the coupling element defined on the bearing pin.
The rectilinear flexible bearing faces on the coupling element can be formed by blades which, at one end, are rigidly connected, in particular integrally, to the coupling element body and, with free ends, project into a recess in the coupling element body. The blades are designed to be flexibly resilient so that the energy-absorbing effect is therefore achieved when the coupling element is subjected to excessive loads.
Additional bearing elements having support faces over a circle round the pivot axis of the coupling element can also be provided. Support faces can also be provided on additional bearing elements on which the coupling element is additionally supported in its engaged position.
Furthermore, the coupling element can rest with an impact energy-absorbing contact face on the belt sensor mass, at least on the lever arm on which the engagement part, in particular in the form of a pawl on the coupling element, is provided. This impact energy-absorbing contact face can also be formed by a resiliently flexible blade which is shaped integrally onto the coupling element.
The coupling device which produces a preblocking state introducing the main blocking process can also have a coupling element, for example in the form of a pawl, mounted movably, in particular pivotally on the control member. This coupling element is brought into coupling engagement with the carrier member, in particular with peripheral teeth on the disc-shaped carrier member by the vehicle sensor mass when an excessive acceleration acts on the vehicle.
Owing to the coupling device, therefore, a preblocking state can be produced between the carrier member preferably designed as a ratchet wheel and the control member preferably forming the outer covering of the preassembled component in the invention. Control member and carrier member are non-rotatably connected to one another so as to transmit a rotation of the reel in the belt webbing uncoiling direction for actuating the blocking device.
The blocking device preferably contains at least one blocking pawl which is supported on the frame and can be brought into main blocking engagement with the belt reel by the control movement of the control member. For this purpose, a control face along which a movement-transmitting element is guided acts between the blocking pawl and the control member. The control face is preferably provided on the blocking pawl and the movement-transmitting element, for example in the form of a pin, on the control member. It is also possible, however, to provide the control face on the control member and the movement-transmitting element on the blocking pawl.
An end stop for the movement of the movement-transmitting element is provided on the control face. This end stop is located in an overtravel position in order to compensate differences in the angular pitch between the teeth participating in the preblocking and main blocking processes.
The preblocking state can obviously also be used in such a way that, in the case of an automatic lift roller device, the belt reel, which is blocked against further rotation during the preblocking process, is engaged by its blocking teeth in opposing teeth provided on the frame.
The control member, the carrier member which can be designed as a ratchet wheel, and the coupling elements, which can be actuated in response to the belt webbing and vehicle, are preferably produced from plastics material. The sensor masses which respond to the belt webbing and the vehicle are traditionally produced from metal.
An embodiment of the invention will be described in more detail with reference to the figures, in which: